1. Field of the Invention
The present invention generally relates to a vehicle tracking system and a vehicle tracking method, and more particularly to a vehicle tracking system and method used for tracking a vehicle at nighttime.
2. Description of the Related Art
Present existing vehicle detection technologies include the methods of using the properties of edges, moving profiles, background convergence or corners to extract the characteristics of the appearance of a vehicle. However, the light at nighttime or a dark place is relatively non-uniform, so that the aforementioned methods cannot be applied in the environment of roads at night time effectively. With reference to FIGS. 1 to 3 for schematic views of a conventional way of detecting vehicles, the result of the edge detection can be observed in the image, and the detected objects on a road surface include automobile lamps, road surface glares, road markings and signs, etc. FIG. 1 shows typical nighttime traffic scenes from an urban road and highway under different environmental illumination conditions. These figures depict that, in typical nighttime traffic scenes, there are moving cars and motorbikes on the road, and under poorly or brightly environmental illuminated conditions, vehicle lights are the only valid salient features. In addition, lamps, traffic lights, and signs are also visible sources of illumination in the image sequences of nighttime traffic scenes. In FIG. 2, the difference between two successive images is used for obtaining a moving profile, and the moving profile is still primarily based on the lamp. In FIG. 3, the background of an image can be obtained by background convergence, and the difference between the original image and the background is used for detecting a foreground object, wherein an image with a higher setting minus the threshold value is used to extract the characteristics of an object which is basically a lamp. In summary, a lamp is a major characteristic of the road environment at nights, regardless of which method is used for extracting the object. Therefore, it is very important to provide a vehicle tracking system that uses a lamp as a basis to overcome the technical issue of the conventional vehicle detection technology that cannot be operated effectively at night time.